Seventy percent of the more than 3,900 respondents said it was somewhat easy or very easy to get the medications without a prescription, such as those prescribed for ADHD.
The 2015 College Prescription Drug Study, conducted by Ohio State University, included undergraduate, graduate and professional students at six public and two private colleges and universities in five states.
The survey found that undergraduates were more likely to misuse prescription drugs. Most claimed they used the drugs to help them study or improve their grades.
About 18 percent of undergraduates said they misused prescription stimulants, and 83 percent said they obtained them from friends.
Stimulant use was the most common practice, but students are misusing a number of other types of prescription drugs.
"Overall, one in four undergraduates reported that they used prescription pain medications, sedatives or stimulants for non-medical reasons in their lifetimes,"
study author Anne McDaniel said in a university news release. McDaniel is associate director of research and data management at Ohio State's Centre for the Study of Student Life.
Pain medications were misused by 10 percent of undergraduates, and about one-third of students said it was easy or very easy to obtain them.
About 9 percent of undergrads misused sedatives, and 44 percent said it was easy or very easy to get them on campus.
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The reasons college students misuse prescription drugs have changed over the years, according to Kenneth Hale, a clinical professor of pharmacy at Ohio State and associate director of its Higher Education Center for Alcohol and Drug Misuse Prevention and Recovery.
"At one time, college students most commonly misused drugs to get high. But today, students also use medications to self-medicate, to manage their lives. They are using drugs to control pain, to go to sleep, to relieve anxiety and to study," he said in the news release.
Fifty-five percent of students who misused pain medications did so for pain relief, while 46 percent did so to get high. More than half who misused sedatives did so to sleep, while 85 percent did so to help them study or improve their grades, according to the survey.